Difference between revisions of "748.2 Roadway Design Criteria"

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[[image:748.2 Photo Roadway Overtopping.jpg|right|450 px]]
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[[Image:748.2 Photo Roadway Overtopping2.jpg|thumb|Flash Flooding on Rt. F Barton County|400 px]]
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On Major Routes, for bridges and boxes, the water level shall be no deeper than 1 foot below the lowest shoulder point during a 50- to 100-year event. For bridges and boxes on interstates use the 100-year event. For pipes, the water level shall be no deeper than 1 foot below the lowest shoulder point during a 25- to 50-year event. For pipes on interstates use the 50-year event.
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==748.2.1 Roadside Ditch and Culvert Frequency Criteria==
  
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On Minor Routes, for bridges and boxes, the water level shall be no deeper than 1 ft. below the lowest shoulder point during a 25- to 50-year event. For pipes, the water level shall be no deeper than 1 ft. below the lowest shoulder point during a 10- to 25-year event.
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See [[:Category:749 Hydrologic Analysis#749.2.1.2 Roadside Ditches and Culverts|EPG 749.2.1.2 Roadside Ditches and Culverts]].
  
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For structural replacements, the upper end of the hydraulic frequency ranges is used for high volume routes and sites requiring only minimal roadway work. The lower end of the hydraulic frequency ranges is used for low volume routes and sites requiring extensive roadway work.  For new locations, consider the expected traffic volumes and length of roadway to be constructed in selecting an overtopping design frequency.  When rehabilitating an existing structure it is not required that the adjacent roadway be raised to meet the roadway overtopping standards for new roads.  The replacement structure should be designed such that it does not increase the frequency of roadway overtopping.
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==748.2.2 Crossroad Structure Frequency Criteria (Roadway Design Frequency)==
  
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The overtopping discharge is the lowest discharge that overtops the lowest point on the roadway. The overtopping frequency is the recurrence interval of the overtopping discharge. The roadway overtopping frequency is documented in the files and labeled on the plans as the “overtopping frequency”. For overtopping frequencies > 500 years, simply report "> 500 years" on the plans. The files include a note indicating that improving the roadway overtopping frequency would have been outside the scope of the project.
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===748.2.2.1 [[media:144 Major Highway System 2022.pdf|Major Routes]]===
  
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==High Water Marks==
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On Major Routes, for bridges and box culverts, the water level shall be no higher than 1 foot below the lowest shoulder point during a 50- to 100-year event. For bridges and box culverts on interstates use the 100-year event. For pipes, the water level shall be no higher than 1 foot below the lowest shoulder point during a 25- to 50-year event. For pipes on interstates use the 50-year event.
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===748.2.2.2 Minor Routes===
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On Minor Routes, for bridges and box culverts, the water level shall be no higher than 1 ft. below the lowest shoulder point during a 25- to 50-year event. For pipes, the water level shall be no higher than 1 ft. below the lowest shoulder point during a 10- to 25-year event.
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===748.2.2.3 New Locations===
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For new locations, consider the expected traffic volumes and length of roadway to be constructed in selecting the roadway design frequency.
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===748.2.2.4 Replacement Structures===
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For structure replacements, the lower end (i.e., 100-year) of the hydraulic frequency ranges is used for high volume routes and sites requiring only minimal roadway work. The upper end (i.e., 25-year) of the hydraulic frequency ranges is used for low volume routes and sites requiring extensive roadway work. The replacement structure should be designed so that it does not increase the roadway design frequency.
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===748.2.2.5 Rehabilitated Structures===
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When rehabilitating an existing structure it is not required that the adjacent roadway be raised to meet the roadway design criteria for new roads.
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===748.2.2.6 Project Scope===
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When applicable, the project file shall include a note indicating that improving the roadway design frequency is outside the scope of the project.
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==748.2.3 Overtopping Flood==
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The [[:Category:749 Hydrologic Analysis#749.2.3 Overtopping Flood|overtopping flood]] is the actual flood at which flow occurs over the roadway. It is used as a design scour event and is the overtopping event reported on the plans.
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==748.2.4 High Water Marks==
 
The districts shall keep a record of the elevation of high water marks during floods for future design purposes. High water marks should be indicated on roadway structures if possible and labeled with the year of the occurrence.
 
The districts shall keep a record of the elevation of high water marks during floods for future design purposes. High water marks should be indicated on roadway structures if possible and labeled with the year of the occurrence.
  
 
[[Category:748 Hydraulics and Drainage|748.02]]
 
[[Category:748 Hydraulics and Drainage|748.02]]

Latest revision as of 07:17, 3 June 2022

Flash Flooding on Rt. F Barton County

748.2.1 Roadside Ditch and Culvert Frequency Criteria

See EPG 749.2.1.2 Roadside Ditches and Culverts.

748.2.2 Crossroad Structure Frequency Criteria (Roadway Design Frequency)

748.2.2.1 Major Routes

On Major Routes, for bridges and box culverts, the water level shall be no higher than 1 foot below the lowest shoulder point during a 50- to 100-year event. For bridges and box culverts on interstates use the 100-year event. For pipes, the water level shall be no higher than 1 foot below the lowest shoulder point during a 25- to 50-year event. For pipes on interstates use the 50-year event.

748.2.2.2 Minor Routes

On Minor Routes, for bridges and box culverts, the water level shall be no higher than 1 ft. below the lowest shoulder point during a 25- to 50-year event. For pipes, the water level shall be no higher than 1 ft. below the lowest shoulder point during a 10- to 25-year event.

748.2.2.3 New Locations

For new locations, consider the expected traffic volumes and length of roadway to be constructed in selecting the roadway design frequency.

748.2.2.4 Replacement Structures

For structure replacements, the lower end (i.e., 100-year) of the hydraulic frequency ranges is used for high volume routes and sites requiring only minimal roadway work. The upper end (i.e., 25-year) of the hydraulic frequency ranges is used for low volume routes and sites requiring extensive roadway work. The replacement structure should be designed so that it does not increase the roadway design frequency.

748.2.2.5 Rehabilitated Structures

When rehabilitating an existing structure it is not required that the adjacent roadway be raised to meet the roadway design criteria for new roads.

748.2.2.6 Project Scope

When applicable, the project file shall include a note indicating that improving the roadway design frequency is outside the scope of the project.

748.2.3 Overtopping Flood

The overtopping flood is the actual flood at which flow occurs over the roadway. It is used as a design scour event and is the overtopping event reported on the plans.

748.2.4 High Water Marks

The districts shall keep a record of the elevation of high water marks during floods for future design purposes. High water marks should be indicated on roadway structures if possible and labeled with the year of the occurrence.

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